1. Field of the Invention
This invention concerns a two cycle internal combustion engine with multiple cylinder fuel injection which controls the amount of fuel injection based on the amount of air intake determined from the pressure in the crank chamber.
2. Description of Related Art
It is known to control the amount of fuel injected in fuel-injected internal combustion engines by detecting the amount of air intake. The method used in the past to detect the amount of air intake was to employ an air flow meter, but this increased the air intake resistance and caused changes in the operating characteristics of the engine. More recently, the amount of air intake has been computed using variations in the pressure inside the crank chamber. This type of arrangement is described in Japan Patent Hei 2-2-4785 (1990). The air intake volume is computed based on the difference between the pressure in the crank chamber immediately prior to the scavenging port opening (SPO) and the pressure in the crank chamber when the scavenging port was closed (SPC). The amount of fuel injection is controlled based on this amount of air intake.
In this prior art example, the rapid change in the pressure inside the crank chamber just after the SPO makes it possible to detect the amount of intake air accurately in order to maintain an optimal air/fuel mixture.
However, in a multiple cylinder type of internal combustion engine, the configuration of the exhaust system could cause a pressure return to the crank chamber due to the blow-down pressure of cylinders between the SPO and the SPC. Also, pressure wave pulses or changes in back pressure in the exhaust system could affect the SPC and make it impossible to determine the difference between the SPO and the SPC, and the expulsion of the combustion gas from the cylinder could vary over the entire operating range, causing the air intake to differ. Therefore, the type of arrangement described in the above-mentioned Japan Patent Hei 2-2-4785 would not be able to accurately detect the air intake volume for a two cycle multiple cylinder internal combustion engine.